Nature and distribution of vascular resistance in hypoxic pig lungs

We used the vascular occlusion technique in pig lungs isolated in situ to describe the effects of hypoxia on the distribution of vascular resistance and to determine whether the resistive elements defined by this technique behaved as ohmic or Starling resistors during changes in flow at constant outflow pressure, changes in outflow pressure at constant flow, and reversal of flow. During normoxia, the largest pressure gradient occurred across the middle compliant region of the vasculature (delta Pm). The major effect of hypoxia was to increase delta Pm and the gradient across the relatively noncompliant arterial region (delta Pa). The gradient across the noncompliant venous region (delta Pv) changed only slightly, if at all. Both delta Pa and delta Pv increased with flow but delta Pm decreased. The pressure at the arterial end of the middle region was independent of flow and, when outflow pressure was increased, did not increase until the outflow pressure of the middle region exceeded 8.9 Torr during normoxia and 18.8 Torr during hypoxia. Backward perfusion increased the total pressure gradient across the lung, mainly because of an increase in delta Pm. These results can be explained by a model in which the arterial and venous regions are represented by ohmic resistors and the middle region is represented by a Starling resistor in series and proximal to an ohmic resistor. In terms of this model, hypoxia exerted its major effects by increasing the critical pressure provided by the Starling resistor of the middle region and the ohmic resistance of the arterial region.

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Distribution of pulmonary vascular pressure as a function of perinatal age in lambs

Journal of Applied Physiology ◽

10.1152/jappl.1989.66.1.79 ◽

1989 ◽

Vol 66 (1) ◽

pp. 79-87 ◽

Cited By ~ 8

Author(s):

M. L. Tod ◽

J. T. Sylvester

Keyword(s):

Pressure Gradient ◽

Pulmonary Vascular Resistance ◽

Vascular Resistance ◽

Vascular Occlusion ◽

Major Change ◽

Major Effect ◽

Middle Region ◽

Prostaglandin F2 Alpha ◽

Fetal Lungs ◽

Isolated Lungs

The distribution of pulmonary vascular resistance (PVR) with respect to compliance was determined using vascular occlusion in isolated lungs from lambs at five ages, from 2 wk before birth to 1 mo of age. The major change in PVR occurred in the pressure gradient across the middle compliant region (delta Pm), which dropped sharply at birth, remained low for 2 wk, and increased at 1 mo. Pulmonary vasoreactivity also varied with ages. Lungs at 0–4 days did not respond to hypoxia and responded poorly to prostaglandin F2 alpha (PGF2 alpha). In contrast, lungs at 13–33 days had significant increases in delta Pm and the gradient across relatively indistensible arterial vessels during hypoxia and increases in all gradients with PGF2 alpha. Ventilation of fetal lungs reduced PVR, mainly because of a 50% reduction in delta Pm. Our results demonstrate that the magnitude and distribution of PVR relative to compliance varied as a function of perinatal age and that pulmonary vasoreactivity depended on postnatal age. The major effect of ventilating fetal lungs was on the middle region.

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Effects of arterial ligation and embolization on pulmonary vascular pressure distribution

Journal of Applied Physiology ◽

10.1152/jappl.1987.63.4.1387 ◽

1987 ◽

Vol 63 (4) ◽

pp. 1387-1395 ◽

Cited By ~ 7

Author(s):

M. L. Tod ◽

M. L. McGeady ◽

P. Rock ◽

J. T. Sylvester

Keyword(s):

Pressure Gradient ◽

Pressure Distribution ◽

Vascular Occlusion ◽

Longitudinal Distribution ◽

Middle Region ◽

Arterial Ligation ◽

Vasomotor Responses ◽

Vascular Compliance ◽

Occlusion Technique ◽

Flow Through

The effects of embolization on the longitudinal distribution of pulmonary vascular pressures with respect to vascular compliance were determined by the vascular inflow and outflow occlusion technique in isolated blood-perfused pig lungs treated with papaverine to prevent vasomotor responses. Embolization with microspheres having mean diameters of 75, 200, and 550 microns and with barrier beads (2 X 3 X 3.5 mm) significantly increased the pressure gradient across the relatively compliant middle region (delta Pm) without increasing the gradients across the relatively noncompliant regions on the arterial (delta Pa) or venous (delta Pv) ends of the vasculature. In contrast ligation of several lobar arteries caused delta Pa to increase from 0.9 +/- 0.3 to 5.9 +/- 1.1 mmHg but did not change delta Pm or delta Pv. Assuming that delta Pa and delta Pv measured by vascular occlusion result from cessation of flow through resistances, these data suggest that in isolated pig lungs the vessels at the boundary between the arterial and middle regions defined by the occlusion technique are arteries greater than 2–3 mm diam and smaller than lobar arteries.

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Sites of inhaled NO-induced vasodilation during hypoxia and U-46619 infusion in isolated lamb lungs

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1995.268.4.h1422 ◽

1995 ◽

Vol 268 (4) ◽

pp. H1422-H1427 ◽

Cited By ~ 1

Author(s):

M. L. Tod ◽

D. C. O'Donnel ◽

J. B. Gordon

Keyword(s):

Pressure Gradient ◽

Pulmonary Veins ◽

Vascular Occlusion ◽

Similar Degree ◽

Pressure Gradients ◽

Small Arteries ◽

Pulmonary Vasoconstriction ◽

Occlusion Technique ◽

Inhaled No ◽

Rapid Binding

The sites of relaxation in response to inhaled nitric oxide (NO) were investigated using the vascular occlusion technique in isolated blood-perfused lungs from 1- to 3-mo-old lambs. In one group of 10 lungs, inhaled NO (45 ppm) was administered during hypoxia- and U-46619-induced pulmonary vasoconstriction. In a second group of 5 lungs, responses to inhaled NO and infused sodium nitroprusside (SNP, 3 micrograms.kg-1.min-1) during U-46619-induced hypertension were compared. Hypoxia caused significant pulmonary vasoconstriction, with increases in the pressure gradients of large and small arteries and small veins, as defined by vascular occlusion. Inhaled NO significantly reduced the total pulmonary pressure gradient by 67% and relaxed both large and small arteries. Infusion of U-46619 caused significant increases in all segmental pressure gradients. While inhaled NO was effective in relaxing the large and small arteries and the small veins, it had no effect on the large veins. Infusions of SNP, a nitrosovasodilator thought to act like endogenous NO, caused a similar degree of total relaxation as NO (81 vs. 77%, respectively). However, in contrast to inhaled NO, SNP was effective in reducing the pressure gradient of the large pulmonary veins. These results suggest that rapid binding to and thus inactivation of inhaled NO by hemoglobin limit its efficacy as a pulmonary venous dilator.

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Effect of hematocrit on vascular pressure profile in dog lungs

Journal of Applied Physiology ◽

10.1152/jappl.1985.58.3.743 ◽

1985 ◽

Vol 58 (3) ◽

pp. 743-748 ◽

Cited By ~ 11

Author(s):

M. Julien ◽

T. S. Hakim ◽

R. Vahi ◽

H. K. Chang

Keyword(s):

Vascular Resistance ◽

Lower Lobe ◽

Blood Flow Rate ◽

Pressure Profile ◽

Venous Occlusion ◽

Longitudinal Distribution ◽

Middle Segment ◽

Pressure Drops ◽

Occlusion Technique

We studied the effect of blood hematocrit (Hct) on the longitudinal distribution of pulmonary vascular pressure profile in an in situ isolated left lower lobe preparation of dog lung using the arterial and venous occlusion technique. The total arteriovenous pressure drop (delta PT) across the lobe was partitioned into pressure drops across an arterial (delta Pa), a venous (delta Pv), and a middle segment (delta Pm). Three levels of Hct were studied: low (18 +/- 5%), normal (41 +/- 4%), and high (66 +/- 5%). Arterial and venous occlusions were performed under constant-flow or constant-pressure perfusion. When flow was maintained constant, the increase in delta PT between low and normal Hct was due to increases in delta Pa, delta Pm, and delta Pv; however, between normal and high Hct, the increase in delta PT was primarily due to an increase in delta Pm. When delta PT was kept constant by adjusting flow, changes in delta Pa and delta Pv were in the same direction as changes in blood flow rate but in opposite direction to changes in Hct. In contrast, changes in delta Pm were in the same direction as changes in Hct. The results showed that the vascular resistance of the middle segment ranged from 7% of total pulmonary vascular resistance at low Hct to 53% at high Hct, suggesting that the vessels within this segment offer the greatest impairment to the transit of blood cells.

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Segmental pulmonary vascular resistance in progressive hydrostatic and permeability edema

Journal of Applied Physiology ◽

10.1152/jappl.1985.59.1.242 ◽

1985 ◽

Vol 59 (1) ◽

pp. 242-247 ◽

Cited By ~ 14

Author(s):

C. G. Wang ◽

T. S. Hakim ◽

R. P. Michel ◽

H. K. Chang

Keyword(s):

Vascular Resistance ◽

Venous Pressure ◽

Lower Lobe ◽

Venous Occlusion ◽

Longitudinal Distribution ◽

Edema Formation ◽

Small Rise ◽

Occlusion Technique ◽

Isolated Lungs

We used the in situ blood-perfused left lower lobe preparation of the dog to examine the effect of hydrostatic and permeability edema on the slope and intercept of the vascular pressure-flow (P/Q) relationship and on the longitudinal distribution of vascular resistance with the arterial and venous occlusion technique. Hydrostatic edema (HE) was induced by raising the venous pressure, and permeability edema (PE) was induced with alpha-naphthylthiourea. When the hematocrit (Hct) of the perfusate was kept normal (approximately 40%), HE had no significant effect on either the slope or the intercept of the P/Q relationship or on the distribution of vascular resistance. PE caused a small increase in the intercept of the P/Q relationship and a small rise in the resistance of the vessels in the middle segment. In another series of HE experiments in which Hct was allowed to increase during edema formation, there was a marked increase in vascular resistance. We conclude that edema per se does not increase vascular resistance significantly and that the increases in vascular resistance which were observed previously by other investigators in the isolated lungs may be due to increases in blood hematocrit.

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Diagnosis of in Situ Air Sparging Performance Using Groundwater Pressure Changes During Startup and Shutdown

10.21236/ada406092 ◽

2001 ◽

Author(s):

Richard L. Johnson ◽

Paul C. Johnson ◽

Tim L. Johnson ◽

Neil Thomas ◽

Andrea Leason

Keyword(s):

Air Sparging ◽

Pressure Changes

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Effect of lung inflation on pulmonary vascular resistance by arterial and venous occlusion

Journal of Applied Physiology ◽

10.1152/jappl.1982.53.5.1110 ◽

1982 ◽

Vol 53 (5) ◽

pp. 1110-1115 ◽

Cited By ~ 51

Author(s):

T. S. Hakim ◽

R. P. Michel ◽

H. K. Chang

Keyword(s):

Pulmonary Vascular Resistance ◽

Vascular Resistance ◽

Venous Pressure ◽

Venous Occlusion ◽

Lung Inflation ◽

Pressure Drops ◽

Constant Flow Rate ◽

Initial Decrease ◽

Occlusion Technique ◽

First Time

To explain the changes in pulmonary vascular resistance (PVR) with positive- and negative-pressure inflation (PPI and NPI, respectively), we studied their effects in isolated canine left lower lobes perfused at constant flow rate. The venous pressure was kept constant relative to atmospheric pressure during lung inflation. The total arteriovenous pressure drop (delta Pt) was partitioned with the arterial and venous occlusion technique into pressure drops across arterial and venous segments (large indistensible extra-alveolar vessels) and a middle segment (small distensible extra-alveolar and alveolar vessels). PPI caused a curvilinear increase in delta Pt due to a large Starling resistance effect in the alveolar vessels associated with a small volume-dependent increase in the resistance of alveolar and extra-alveolar vessels. NPI caused an initial decrease in delta Pt due to reduction in the resistance of extra-alveolar vessels followed by an increase in delta Pt due to a volume-dependent increase in the resistance of all vessels. In conclusion, we provided for the first time evidence that lung inflation results in a volume-dependent increase in the resistance of both alveolar and extra-alveolar vessels. The data suggest that while the volume-related changes in PVR are identical with PPI and NPI, there are pressure-related changes that can be different between the two modes of inflation.

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Identification of Compensatory Arterial Dynamics in Swine Using a Non-Invasive Sensor for Local Vascular Resistance

Volume 1: Advances in Control Design Methods; Advances in Nonlinear Control; Advances in Robotics; Assistive and Rehabilitation Robotics; Automotive Dynamics and Emerging Powertrain Technologies; Automotive Systems; Bio Engineering Applications; Bio-Mechatronics and Physical Human Robot Interaction; Biomedical and Neural Systems; Biomedical and Neural Systems Modeling, Diagnostics, and Healthcare ◽

10.1115/dscc2018-9063 ◽

2018 ◽

Author(s):

Lu Wang ◽

Sardar Ansari ◽

Kevin R. Ward ◽

Kayvan Najarian ◽

Kenn R. Oldham

Keyword(s):

Cardiovascular System ◽

Vascular Resistance ◽

Systemic Circulation ◽

Test Subject ◽

Loop Model ◽

Peripheral Vascular ◽

Dynamics Model ◽

Non Invasive ◽

Peripheral Arterial ◽

Pressure Changes

Autoregulatory dynamics of the cardiovascular system play an important role in maintaining oxygenated blood transportation throughout the human body. In this work, a feedback dynamics model of the cardiovascular system with respect to heartrate and peripheral vascular resistance effects on longer-term blood pressure changes in the systemic circulation is presented. The model is identified from data taken from a swine test subject, instrumented in part with a wearable, non-invasive sensor for estimating peripheral arterial radius. Comparative simulations for the open and close loop model highlight significantly changed hemodynamics after hemorrhage.

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AMPLIFIER DESIGN FOR MODELING THE TRANSMISSION OF A DIGITAL VIDEO SIGNAL OVER A DATA TRANSMISSION CHANNEL

NEWS of National Academy of Sciences of the Republic of Kazakhstan ◽

10.32014/2021.2518-170x.6 ◽

2021 ◽

Vol 445 (1) ◽

pp. 39-45

Author(s):

M. Amreev ◽

R. Safin ◽

T. Pavlova ◽

E. Temyrkanova ◽

Y. Garmashova

Keyword(s):

Transmission Line ◽

Video Surveillance ◽

Video Transmission ◽

Main Task ◽

Surveillance Systems ◽

Video Signals ◽

Ohmic Resistance ◽

In Series ◽

Amplifier Design

The use of video surveillance systems is used in the areas of security, law and order, in the territories of protected objects, in monitoring the movement of road vehicles and in other areas. The main disadvantage of a video surveillance system is its susceptibility to weather influences (rain, fog, snowfall, etc.), which degrades the quality of the video system by reducing the signal level. Therefore, the urgency of finding new ways and possibilities to improve the quality of video signals is one of the priority areas of signal processing. The main task of this work was to determine the main parameters, simulate the transmission line and amplifier, and select the schematic diagram of the transmitting and receiving path with the voltage and current ratings. Both the receiver and the cable video transmitter have different means of adjusting to different transmission line lengths. The signal at the output of each receiver should be in the range from 0.9 to 1.1 V, and the spread of the total ohmic resistance of the wires of the video transmission line at the input of the receiver should be no more than 2 – 3%. Based on these parameters, the equipment is configured for transmitting video over the channel. The magnitude of the mismatch is regulated by potentiometers, which allow smooth adjustment of the video transmission equipment [1]. As a rule, video transmission over the channel is carried out at a distance of 50 to 1500 m. If it is necessary to transmit video at distances less than 50 m, additional resistances are connected in series at the receiver input so that the total line resistance is 30 - 50 Ohm [1].

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